Electric motors having an outer rotor configuration have a stator arrangement made up, for example, of a number of stacked stamped metal laminations which form an annular stator back yoke and stator teeth that protrude outwards from the stator back yoke. Phase windings are mounted on the stator teeth. The stator arrangement is inserted coaxially into a rotor arrangement. As a rule, the rotor arrangement comprises a back yoke ring on whose inside circumference one or more magnets are mounted. The magnets may also be embedded in the rotor body.
In the manufacture of stator arrangements for inner or outer rotor motors from stacked stamped metal laminations, there is always a certain amount of material waste, the useful electromagnetic surface being significantly smaller than the surface of the blank. This problem is particularly serious for outer rotor motors having a large diameter because the stator rings generally have a relatively large inside circumference, the inner circle of the respective sheet metal blank remaining unused. If the inside core of the stator were not cut away, this would result in a considerable increase in the weight of the motor, which is equally undesirable.
In the prior art, stator arrangements have been developed that comprise a multi-part stator body. Stator bodies are known in which each stator tooth forms an individual component and the stator teeth are either directly connected to one another or connected via a separate ring. The individual stator teeth are inserted one inside the other in the way of tongue and groove joints, for example, and kept together by an interference fit. It is also known to slide individual stator teeth onto a stator back yoke ring. Examples of these kinds of multi-part stators can be found in U.S. Pat. No. 6,359,335; WO 02/47238; U.S. Pat. No. 5,786,651; DE 198 42 948; EP 0 915 553; U.S. Pat. No. 6,049,153; U.S. Pat. No. 5,796,195; EP 1 014 536; WO 02/47240; U.S. Pat. No. 6,555,942 and DE 101 43 870. In these kinds of multi-part stators, each stator tooth, or pole shoe respectively, can be wound separately and subsequently connected to the other stator teeth. The advantage of a multi-part stator body is that the individual parts can be produced with less waste. Particularly when each section includes a pole shoe, each pole shoe can be so configured that it receives a prefabricated coil. When the coils have been mounted onto the respective pole shoes, the stator sections are connected to each other and so arranged that, together with a stator back yoke ring, they form the complete stator. The greater proportion of the above-mentioned documents relate to inner rotor motors.
Applying phase windings to multi-part stator arrangements is easier than winding conventional single-part stator arrangements for outer or inner rotor motors. Although the prefabricated coils have to be mounted and connected in an extra production step, winding the stators is nevertheless made easier and quicker as a whole thanks to the possibility of using prefabricated coils. The use of thick coil wires in combination with thin pole gaps is made particularly easy using multi-part stator arrangements.
The problem arising in the manufacture of multi-part stator arrangements is that the individual stator teeth have to be connected together and held together in an appropriate way. This has generally been solved in the prior art by mounting the stator teeth onto a continuous stator ring. In other known embodiments, the stator teeth are coupled to each other using tongue and groove joints or similar means.
It is an object of the invention to provide a stator arrangement for an electric machine, particularly an outer rotor motor, that has a simple construction, that is manufactured with little waste and which can be wound and assembled with out any problems.